1. Field of the Invention
The present invention relates to a facsimile apparatus for communicating information by over public telephone networks.
2. Description of the Related Art
While some facsimile apparatus incorporate multiple telephone functions, others do not. When a telephone function is not incorporated, an external telephone set is often connected to an extension telephone terminal (modular jack) provided in the facsimile apparatus. The external telephone set many include various functions such as, for example, an automatic telephone answering function for automatically responding to a call transmitted over the network if the callee is absent, and storing the voice message of the caller.
A facsimile apparatus having such an external telephone terminal generally operates in three reception modes; a manual reception mode, an automatic reception mode, and an answering telephone connection mode. The user selects the mode. In the manual reception mode, the user lifts the handset of an internal or external telephone set, responds to the call, and manually changes to the facsimile reception, e.g. by pressing a start button or the facsimile machine. In the automatic reception mode, after the apparatus automatically reacts to the call, a determination is made whether the call is a facsimile reception or a voice message, the communication is connected to the appropriate receiving unit.
In the answering telephone connection mode, the connected telephone set executes an automatic telephone answering function and judges if a predetermined condition has occurred, the connection of the public telephone line is automatically changed to the facsimile apparatus after the automatic telephone answering function is completed. The predetermined condition may correspond to the absence of a caller's voice message to be recorded after the answering machine has generated a prompt to leave a message "after the beep," i.e., a no-signal state for a specific period.
FIG. 9 is a timing chart showing the operation of a conventional facsimile apparatus combined with a telephone set with automatic telephone answering function as mentioned above. An incoming signal A (i.e., a ring signal) shown in FIG. 9 (1) is received through the public telephone network, and when the incoming signal A is received a predetermined number of times, i.e., a predetermined number of rings, for example, two times as shown in FIG. 9 (1), the automatic telephone answering function of the connected telephone set is activated as shown in FIG. 9 (2), a voice amendment message B is sent out. The voice message B says, for example, "I'm away from home now. Leave your message after the beep sound." After a specific no-signal period, a dial tone D or beep indicating the start of recording is generated, and the caller's message E is recorded for a predetermined time t1, for example, 30 seconds or a minute. When recording for the time t1, a dial tone G or beep indicating the end of recording is generated.
When the facsimile apparatus is set in the manual reception mode as shown in FIG. 9 (3), whether during or after operation of the automatic telephone answering function, the public telephone network remains connected to the telephone set. Or, as shown in FIG. 9 (4), when the telephone set is in the answering telephone connection mode, by detecting the state H in which the signal level is -48 dBm or less for a predetermined no-signal period t2 during operation of the automatic telephone answering function, the connection of the public telephone circuit is automatically changed over to the facsimile apparatus.
A problem arises when the facsimile apparatus is in the manual reception mode, and the public telephone circuit remains connected to the telephone set rather than being changed over to the facsimile apparatus automatically. Using only a single telephone line it is impossible to operate both the facsimile reception and the automatic telephone answering function by the telephone set at the same time. In a facsimile apparatus conforming to the recommendation of the CCITT (International Telegraph and Telephone Consultative Commitee), a CNG control signal transmitted from the facsimile apparatus of the caller, solves this problem by automatically connecting the public telephone network to the receiving facsimile apparatus when receiving the CNG signal. But there are many facsimile apparatus not capable of transmitting the CNG signal. In addition, if the automatic telephone answering function of the telephone set is deactivated when the facsimile apparatus detects the state H corresponding to the no-signal period while the telephone set is actually in service, the public telephone network is automatically changed over to the facsimile apparatus, and the service is interrupted.